I'm not really sure what you were reading - that may have been true through mid-July but once they dumped all those games after the All-Star break they were definitely in discussions about him, but no one was going to take most/all of his contract and give top prospects in return. It did come out right before the deadline that they weren't dealing him, but that was after they kicked the tires. And since there's no rush to deal him, why force it? Since there was no one desperate to trade for him now, his value doesn't go down significantly in the offseason - he's got two more guaranteed years and a club option for a 3rd.
Of course none of the other guys but Hamels have that kind of value, but they had several guys who are going to be free agents, who likely won't be back, and could be potentially useful to a contender, so I'm not sure why you hang on to them. You're not expecting a windfall for any of them, but maybe you hit a jackpot.